A typical bale wrapping mechanism of the prior art includes a filament dispensing apparatus having a pair of dispensing tubes that are movable in an arcuate path downwardly toward and lengthwise of a bale. After a bale has been formed in a bale forming chamber, the dispensing tubes are extended so that the filament is caught up by, and wrapped around the rotating bale in a circular pattern of starting wraps. The dispensing tubes then move lengthwise of the bale toward its ends so that the filament is helically wrapped around the bale. Periodically, the dispensing arms stop or dwell so that circular wraps are made around the bale. Typically, circular wraps are made near each end of the bale and at one or more locations intermediate the end wraps and the starting wraps. After a wrapping operation is completed, the dispensing arms are retracted to a home or cut position where the filament is cut, thus separating the twine supply from the portions which have been wrapped around the bale.
The aforementioned patent to Strosser et al. discloses a microprocessor based control system for automatically controlling the wrapping of round bales with a filament. The system is operable in a learning mode wherein the operator manually controls the filament dispensing mechanism by selective actuation of "extend" and "retract" buttons or switches on an operator's control panel. The microprocessor stores commands representing the switch actuations and the intervals they are actuated. Subsequently, when an operator desires to wrap another bale, he merely actuates a "tie" or "wrap" switch on the control panel. The microprocessor then automatically controls wrapping of the bale in accordance with the signals stored during the learning mode.
Commercially available models of balers employing the Strosser et al. control system are also provided with three factory installed filament wrapping programs. These programs typically provide for 14 to 24 total wraps of a bale, including two starting wraps and two wraps at each end of the bale.
Yves et al. U.S. Pat. No. 4,624,179 discloses two embodiments of a bale wrapping control system, one embodiment being quite similar to the Strosser et al. device described above. In a another embodiment, two thumbwheel switches are provided: one for setting the limit of bale diameter and one for selecting the total number of wraps to be placed on each bale. From this information, a microprocessor computes the required number of dwells and the required period of each dwell in order for the bale to be wrapped by the total number of wraps set on one of the thumbwheels.
It is desirable that the number of wraps made around a bale be kept to a minimum to conserve filament and to reduce the wrapping time. For most bale wrapping operations, two wraps at each end (with intermediate wraps as described above) are sufficient to maintain the integrity of the bale during handling and storage. However, it has been found that the integrity of bales of spongy or stalky crop material with high expansion characteristics cannot be reliably maintained with just two end wraps. The end wraps do not always keep the ends of the bale tight and the filament eventually slips off the end of the bale. Such end wrap failures cause bale handling difficulties or loss of the bale during transport.
Obviously, it is desirable that the operator be able to quickly and easily change the number of end wraps placed on bales. However, this is not possible in the prior art systems described above. In the Strosser et al. system, and one embodiment of the Yves et al. system, the operator must place the system in the learning mode and then selectively and repeatedly actuate the extend and retract switches to cycle the wrapping mechanism through a complete bale wrapping operation. The process must be repeated when the operator desires to change back from a pattern of more than two end wraps to a pattern of just two end wraps. In the alternate embodiment described in the Yves et al. patent, the number of wraps is changed by adjusting a thumbwheel. However, this adjustment changes the total number of wraps, not just the number of end wraps.